This paper presents entropy generation analyses for the evaporator, compressor, gas cooler, expansion device and liquid-line suction-line heat exchanger for a transcritical carbon dioxide cycle for automotive and residential air-conditioning systems, and presents entropy generation analyses for the evaporator, compressor, condenser, and expansion device for a subcritical R134a automotive air-conditioning system and a subcritical R22 residential air-conditioning system. The analyses show that the CO{sub}2 automotive air-conditioning system generates 36% more entropy than the R134a automotive air-conditioning system, and that the CO{sub}2 residential air-conditioning system generates 63% more entropy than the R22 residential air-conditioning system. The biggest contributors to the lower CO{sub}2 performance are irreversibilities associated with the heat rejection process and the expansion related processes.
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